In receivers for storage and communication systems, the output signal of a receive filter is scaled and sampled prior to performing symbol-by-symbol or symbol sequence detection, as described by several authors, e.g. H. Kobayashi in "Simultaneous Adaptive Estimation and Decision Algorithm for Carrier Modulated Data Transmission Systems", IEEE Trans. Commun., vol. COM-19, pp. 268-280, June 1971, and G. Forney, "Maximum-Likelihood Sequence Estimation of Digital Sequences in the Presence of Intersymbol Interference", IEEE Trans. Inform. Theory, vol. IT-18, pp. 363-378, May 1972, and G. Ungerbock, "Adaptive Maximum-Likelihood Receiver for Carrier-Modulated Data-Transmission Systems", IEEE Trans. Commun., vol. COM-22, pp. 624-636, May 1974. A gain control and a timing-recovery scheme adjust the receiver gain and sample-timing phase to minimize sample-amplitude errors and undesired intersymbol interference; a scheme for the adjustment of the timing phase is described in the article of K. H. Mueller and M. Muller, "Timing Recovery in Digital Synchronous Data Receivers", IEEE Trans. Commun., vol. COM-24, pp. 516-530, May 1976.
The present invention relates to magnetic/magneto-optic recording or communication systems using partial-response (PR) signaling. A general description of PR signaling principles is given by P. Kabal and S. Pasupathy in "Partial-Response Signaling", IEEE Trans. Commun., vol. COM-23, pp. 921-934, September 1975. The application of PR signaling in combination with maximum-likelihood sequence detection (MLSD) in storage systems to increase recording densities has been proposed by H. Kobayashi in "Application of Probabilistic Decoding to Digital Magnetic Recording Systems", IBM J. Res. Develop., vol. 15, pp. 64-74, January 1971. For fast initial adjustment of the gain and timing phase in receivers for systems using PR signaling, a synchronization preamble is sent prior to user data. A fast algorithm for the timing-phase adjustment is described in the European Patent Application 87116783.9, "Fast Timing Acquisition for Partial-Response Signaling", and in the article "Fast Timing Recovery for Partial-Response Signaling Systems", Proc. IEEE Int. Conf. on Communications, Boston, pp. 573-577, June 1989, of F. Dolivo, W. Schott, and G. Ungerbock. The above named article of F. Dolivo et. al. is considered the nearest prior art.
The present invention relates in particular to a method for fast and reliably recognizing in binary PR class-IV signaling systems that synchronization has been achieved and the preamble is being received, and to detect the end of preamble. No prior art is known disclosing the method of preamble recognition and synchronization detection of the present invention.